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Mar 21, 2021 at 21:58 vote accept Albert.Lang
S Mar 21, 2021 at 21:58 history bounty ended Albert.Lang
S Mar 21, 2021 at 21:58 history notice removed Albert.Lang
Mar 16, 2021 at 20:42 answer added loopy walt timeline score: 5
S Mar 16, 2021 at 6:24 history bounty started Albert.Lang
S Mar 16, 2021 at 6:24 history notice added Albert.Lang Draw attention
Mar 14, 2021 at 12:00 comment added justhalf "A regicide score in the high 20s should not be a problem". I guess you made it sound easy, while I spent so much time fixing the loophole to get to my solution, lol.
Mar 13, 2021 at 6:01 comment added loopy walt Argh, It's mutating! Very resourceful, @Albert.Lang! And I agree, it is a rather different beast now.
Mar 12, 2021 at 9:36 answer added justhalf timeline score: 7
Mar 12, 2021 at 8:49 comment added Albert.Lang @justhalf Nothing at the moment. But for example d8 makes the pawns occupying the squares it could have come from accessories. So one would have to add a piece that could not have moved but could have if d8 were accessible to make d8 an accomplice.
Mar 12, 2021 at 8:37 comment added justhalf Nice. What makes Nd8 (and Na1) an accessories?
Mar 12, 2021 at 8:35 history edited Albert.Lang CC BY-SA 4.0
deleted 9 characters in body
Mar 12, 2021 at 8:29 comment added Albert.Lang @justhalf I moved the d7 knight instead to keep it as simple as possible. Now the c6 (and e6) pawns could have come from d7, so it will work as originally intended, unless I missed something else, this retrograde stuff is tricky as hell. Re the 30: I almost but not quite managed, so my guess is it is possible. High 20s definitely is.
Mar 12, 2021 at 8:26 history edited Albert.Lang CC BY-SA 4.0
Finally fixed example, I hope
Mar 12, 2021 at 8:21 comment added justhalf Ah, promotion, that's right. There are many black pieces missing that it is possible. But with the Bf1 trapped, you can just remove either of f2 or h2?
Mar 12, 2021 at 8:14 comment added Albert.Lang @justhalf Argh, you are right, the example doesn't work because we would have needed two captures. One to get a second pawn to the b file (and then another one from b7 to a6 or c6. So I need to remove another white piece without breaking everything. Re f2 and h2, don't forget they could have been promoted before being captured.
Mar 12, 2021 at 7:59 comment added justhalf I think in your example, f2 is a witness? It still doesn't allow Bf1 to get out, and it doesn't provide any opportunity for black pawn to capture into any of the position in the final position without invalidating the double move as the last move. Because there is only one pawn capture by black, and the pawns on columns a and c couldn't have captured from column b since there couldn't be a double pawn in column b in the previous move. And perhaps similar argument can be made for h2 pawn as well, since it's too far from the black pawn structure on columns a, b, c.
Mar 12, 2021 at 7:49 comment added justhalf Ah, great example! Although I believe that technically loopy's question still subsumes this, but I agree that this is a viable separate question, like you noted about loopy's intention. Really nice about incorporating retrograde analysis here, as usually all pieces in retrograde analysis are crucial, haha. So maximum score here is 30?
Mar 12, 2021 at 7:28 history edited Albert.Lang CC BY-SA 4.0
fixed example
Mar 12, 2021 at 7:22 comment added Albert.Lang @justhalf I've added an example that I think demonstrates what I mean. To say that the pawns e2 and g2 are actively participating in the checkmate is a bit of a stretch, but they are clearly accessories by the formal definition.
Mar 12, 2021 at 7:19 history edited Albert.Lang CC BY-SA 4.0
added 790 characters in body
Mar 12, 2021 at 6:35 comment added Albert.Lang @justhalf Technically, you are, of course, correct. But the whole "remove one piece at a time and check again" business was originally just a way to get a handle on the vague idea "every piece has a role in the checkmate". Now, having an actual role (like blocking a piece from capturing a checking piece) and being a clue in a retrograde analysis to show that the last move couldn't have been anything other than a given pawn's double move are very different and I think it is fair to assume the latter was not on loopy walt's mind at the time.
Mar 12, 2021 at 6:15 comment added justhalf Hm, if I understand this correctly, it's only adding the requirement to use en passant in the solution? If that's the case, I feel like it's not a loophole. But perhaps I missed something here.
Mar 12, 2021 at 5:03 comment added Albert.Lang @justhalf Yes, as it relies on a loophole in the rules and feels very different in spirit. Also I thought it was more fun to see what you people can do instead of running away with that little "cheat".
Mar 12, 2021 at 3:05 comment added justhalf So, you found a better solution to the other puzzle, but decided to post it as a riddle instead?
Mar 11, 2021 at 23:30 history asked Albert.Lang CC BY-SA 4.0